This invention relates generally to manufacturing of parts having a curved profile, and more particularly to methods and apparatus for machining formed parts that are particularly suited, but not limited to, the manufacturing of airfoils.
An airfoil chord and length trimming operation is performed during manufacturing of compressor blades or vanes. This process produces square burred edge shapes that are aerodynamically unacceptable. The leading edge shape of the airfoil is formed in a secondary operation to produce a radiused leading edge that is aerodynamically acceptable. Acceptability of the leading edge shape is determined by comparing the shape of the airfoil leading edge shape against a predetermined required aerodynamic shape in the form of a reticule. Reticules are created for each required inspection section from an aerodynamic glass master. There is an applicable machining tolerance that allows variation in accordance with the capability of the process.
At least two known methods are currently used to produce leading edge aerodynamic profiles. The first method is a manual operation in which an operator holds onto the part and presses the airfoil edge against a rotating abrasive wheel or belt while moving it through a series of motions to generate the correct edge shape. Edges are then tumbled in an abrasive medium for further rounding. Disadvantages of this method include variability in the consistency of the edge profile and the time required to perform the task, both of which depend upon the skill level of the operator.
A second known method effectively replaces the operator in the first method with a six-axis machine or robot, which is also used in conjunction with a secondary tumble process in an abrasive medium. Multiple passes have been necessary to remove sufficient material before the secondary tumble process can be used to produce the required aerodynamic shape, because satisfactory approximations have not been available to generate sufficiently accurate edge profiles.